Patent Application
20160041204
The field of the invention relates generally to sensor devices and methods and, more particularly, sensing current through a conductor.
At least some known utility meters are used to measure electricity supplied from a power source to a user. To enable an amount of energy supplied to a user to be accurately measured, utility meters often include one or more sensor devices to sense current flowing through a conductor between the power source and the user. When included in a utility meter, the sensor device is intended to function accurately over an operating range of voltages and/or currents.
Various types of known current sensor devices are used in utility meters. For example, at least some known transformer sensor devices include a magnet core with magnet wire wound thereon to sense current flowing through a conductor. Current sensor devices including transformers, however, are generally known to be bulky and expensive. Current sensor devices with magnetic cores are vulnerable to external magnetic fields. Exposure to external magnetic fields reduces the accuracy of magnetic core current sensor devices, in some cases to as the point where the current device only registers as little as 8% of the current that the current device is supposed to be sensing. Temperature cycles may also affect the magnetic core of current sensors and cause magnetic drift which reduces the accuracy of the current sensor.
Another example of a known current sensor device is a Rogowski coil. Rogowski coils include a coil and are generally smaller than transformer sensor devices. However, Rogowski coils are known to provide only limited accuracy during low current and/or high current conditions over a range of voltages. As a result, during manufacturing, utility meters with known Rogowski coils are often subjected to multiple calibration processes to minimize the effects of these inaccuracies. Although these repeated calibration processes may reduce the inaccuracies of such sensor devices, the processes also increase manufacturing times and costs of the utility meters.
In one embodiment, a sensor device for use in detecting current in a conductor is provided. The sensor includes a non-magnetic substrate defining an aperture structured to receive a conductor therein, a coil comprising a plurality of turns wound about at least a portion of the substrate, and a housing for enclosing the substrate and coil. The housing includes a dielectric material having a dielectric constant and positioned adjacent to the coil and at least partially within the aperture such that the dielectric material is disposed between the coil and the conductor when the conductor is received through the aperture and at least one spacer coupled to the aperture to facilitate maintaining a position of the coil relative to the conductor, wherein each of the spacers is positioned offset from the dielectric material such that each of the spacers does not radially extend between the coil and the conductor.
In another embodiment, a utility meter for use in transmitting electrical energy from a power source to a user is provided. The utility meter includes a first sensor device positioned at least partially around a first conductor to sense a current flowing through the first conductor and to output a signal representative of the sensed current and a meter control board in communication with the first sensor device to receive the signal representative of the sensed current from the first sensor device and to determine an amount of electricity transmitted through the conductor from the power source to the user over time;. The first sensor device includes a non-magnetic substrate defining an aperture structured to receive the first conductor therein, a coil comprising a plurality of turns wound about at least a portion of the substrate, and a housing for enclosing the substrate and coil. The housing includes a dielectric material having a dielectric constant and positioned adjacent to the coil and at least partially within the aperture such that the dielectric material is disposed between the coil and the first conductor when the first conductor is received through the aperture and at least one spacer coupled to the aperture of the housing to facilitate maintaining a position of the coil relative to the first conductor, wherein each of the spacers is positioned offset from the dielectric material such that each of the spacers does not radially extend between the coil and the first conductor. The first sensor device is positioned relative to the first conductor to consequently reduce a sensitivity of the first sensor device such that the meter control board comprises only one calibration coefficient for calibrating the first sensor device over a current range, where the current range is about 0.2 A to about 25,000 A.
In yet another embodiment, a method of fabricating a utility meter for use in transmitting electrical energy from a power source to a user is provided. The method includes providing a first sensor device positioned at least partially around a first conductor to sense a current flowing through the first conductor and to output a signal representative of the sensed current, wherein providing the first sensor device includes forming a coil comprising a plurality of turns wound about a non-magnetic substrate where the coil defines an aperture through which the first conductor is to be received and enclosing in a housing the coil and substrate. Enclosing in the housing includes positioning a dielectric adjacent to the coil and at least partially within the aperture such that the dielectric material is disposed between the coil and the first conductor when the first conductor is received through the aperture and positioning at least one spacer at the aperture of the housing to facilitate maintaining a position of the coil relative to the first conductor, wherein each of the spacers is positioned offset from the dielectric such that each of the spacers does not radially extend between the coil and the first conductor. The method further includes connecting a meter control board with the first sensor device to receive the signal representative of the sensed current from the first sensor device and to determine an amount of electricity transmitted through the first conductor from the power source to the user over time, and positioning the first sensor device relative to the first conductor to consequently reduce a sensitivity of the sensor device such that the meter control board comprises only one calibration coefficient for calibrating the sensor device over a current range, where the current range is about 0.2 A to about 25,000 A.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.
The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that may permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
The sensor systems described herein provide efficient sensing of current through conductors. The embodiments described herein use a sensor with contains a coil in contact with a dielectric material to sense current through a conductor. The coil and the dielectric material are formed in a toroid around an aperture such that the conductor can be placed through the aperture. The dielectric material in combination with the coil improves the accuracy of the sensor device, such that the sensor device requires one calibration to achieve a high level of accuracy (±0.2%) during the manufacturing process. However, this level of accuracy is depending on the coil not moving in relation to the conductor.
To prevent the coil from moving the sensor device also includes a housing. In the exemplary embodiment, the housing is made of the dialectic material. In other embodiments, the housing encases the dielectric material. The housing includes spacers to hold the conductor in the aperture in a friction fit, and a rotational positioner to prevent the sensor device from rotating. The spacers are positioned offset from the aperture to prevent additional material from being positioned between the coil and the conductor.
In the exemplary embodiment, the housing comprises two portions that are coupled together using U-clips. The two portions of the housing are formed such that the retaining portions are recessed and when coupled to the clips, the clips are flush with the walls of the housing.
The housing also includes an epoxy for coupling the coil to the dielectric material, where the clips are used to hold the coil in place while the epoxy sets. The two parts of the housing are designed to couple in a ship-lap joint, where sides of the housing overlap and the join forms an S shape. By using a ship-lap joint the sides of the housing keep a consistent thickness of dielectric material, while creating a longer path for arc discharges to travel along. The corners of the housing at the aperture are angled and are tapered in thickness to control the amount of dielectric material between the coil and the conductor.
By preventing the coil from moving in relation to the conductor, the accuracy of the sensor device will not change over time. In a meter, where there may be multiple conductors and multiple sensor devices, preventing the sensor device from moving in the electromagnetic fields in relation to the other conductors and the other sensor devices will also prevent the sensor's accuracy from changing over time.
Because a charge may be incurred for electricity transferred from the power source to the user, it is desirable that sensor device 112 is highly accurate to ensure the user is charged substantially only for electricity received, rather than being charged for substantially all the electricity transmitted to the user by the operator of the power source.
In this exemplary embodiment, utility meter 110 further includes conductors 115 and 116 and another sensor device 112 coupled to conductor 115. It should be appreciated that any number of conductors and/or sensor devices (e.g., one, three, six, etc.) may be used in other utility meter embodiments. Moreover, it should be appreciated that sensor device 112 is not limited to only being used within utility meter 110, but may be utilized in virtually any application to sense current through a conductor, such as power generation applications, utility applications, automotive applications, appliance applications, telecommunication applications, etc.
Dielectric material 208 may include one or more dielectric materials having a variety of characteristics configured in a variety of ways. Dielectric material 208 has at least one thickness, and may have various thicknesses. In the exemplary embodiment, dielectric material 208 positioned adjacent to coil 204 and at least partially within aperture 210 has a thickness of about 3.0 millimeters. Also, in the same embodiment, dielectric material 208 positioned adjacent to coil 204 but opposite aperture 210 has a thickness of about 1.2 millimeters. It should be appreciated that dielectric material 208 may have any thickness or thicknesses, that enables sensor device 112 to function as described herein. Generally, thickness of dielectric material 208 is selected, at least partially based on the dielectric constant of dielectric material 208, the proximity of coil 204 to one or more conductors 114, 115 and 116 (shown in
In the exemplary embodiment, dielectric material 208 may be fabricated from one or more of several types of material, such as, without limitation, plastic materials, thermoplastic materials, thermoset materials, ceramic materials, metallic materials, wood materials, clay materials, organic materials, any mixture thereof, and/or other materials suitable to perform as described herein. In the exemplary embodiment of
The reduction in capacitance enables sensor device 112 to sense current flowing through conductor 114 with improved accuracy, as compared to known Rogowski coils or other air-gap coils. More specifically, by reducing capacitance coupling between coil 204 and conductor 114, the sensitivity to operating voltage is reduced. As a result, consistent current sensing is provided at different operating voltages across a range of different currents, including high and low currents. Accordingly, when sensor device 112 is included in utility meter 110 (shown in
Over time, movement of coil 204 in reference to conductor 114 will affect the calibration of sensor device 112. Preventing coil 204 from moving ensures that the calibration coefficient previously calculated during the calibration process will continue to provide accurate readings from sensor device 112. Movement could be laterally along conductor 114, rotationally moving coil 204 around conductor 114, or even movement of coil 204 itself within sensor device 112.
As shown in
In some embodiments, housing 312 may include one or more materials in addition to dielectric material 208, such as non-dielectric materials or dielectric materials that have different characteristics. In one embodiment, housing 312 includes dielectric material 208 and an additive material, which is provided to support dielectric material 208 in one or more locations relative to coil 204 to enable it to perform as described herein. The additive material may include plastic materials, thermoplastic materials, thermoset materials, ceramic materials, metallic materials, wood materials, clay materials, organic materials, any mixture thereof, and/or other suitable materials. The additive material may be selected based on manufacturing techniques, dimensional stability, cost, moldability, workability, rigidity, and/or other characteristics of the material, etc. In such embodiments, when dielectric material 208 is a higher cost material (as compared to the additive material); the inclusion of an additive material may reduce the overall cost of sensor device 112. Further, one or more additive materials may be used to perform one or more additional functions, such as supporting dielectric material 208, protecting and/or insulating coil 204, etc. As should be apparent, the additive material may be used as part of housing 312 in various embodiments. In the exemplary embodiment, however, an additive material is omitted, as housing 312 substantially only includes dielectric material 208.
Housing 312 may be fabricated from the dielectric material, formed integrally from dielectric material 208 and at least one additive material, or assembled from separate dielectric material(s) 208 and additive material(s). Housing 312 and/or dielectric material 208 may be fabricated using one or more injection molding processes and/or other suitable fabrication processes. In the exemplary embodiment, housing 312 is constructed via a single injection molding process, in which dielectric material 208 is injected into a mold structured to form housing 312.
Alternatively, housing 312 may be constructed from a multi-stage injection molding process. In a multi-stage process, an additive material is molded into a specific shape through an initial molding process. Subsequently, the molded additive material is positioned within a mold, and dielectric material 208 is injected into the mold. Dielectric material 208 flows into voids defined between the mold and/or the additive material, to form housing 312 from dielectric material 208 and additive material. In various embodiments, a multi-stage molding process may permit a relatively high-cost dielectric material to be specifically positioned relative to coils 204 such that desired performance as described herein is achieved, while still permitting other portions of housing 312 to be constructed from one or more relatively low cost materials.
It should be appreciated that housing 312 may be constructed by other fabrication techniques to provide dielectric material 208 throughout or at desired positions relative to coil 204 and/or conductor 114. In one example, dielectric material 208 is constructed separately from an additive material, and subsequently transformed and/or constructed with the additive material to form housing 312. In yet another example, a tubular dielectric material may be inserted into an aperture formed by an additive material to form housing 312.
In the exemplary embodiment, housing 312 includes one or more spacers 316 that surround the aperture 210. When conductor 114 is received in aperture 210 (as shown in
Housing 312 also includes at least one rotational positioner 320. Rotational positioner 320 prevents coil 204 from rotating around conductor 114. The position of coil 204 in relation to conductor 114 and to conductors 115 and 116 affects the accuracy of sensor device 112, when sensor device 112 is surrounding conductor 114. Rotating coil 204 in the electromagnetic fields generated by those conductors can affect the calibration of sensor device 112 and thus the accuracy. To prevent the possibility of rotation of coil 204, housing 312 includes rotational positioner 320. Rotational positioner 320 prevents rotary movement when placed against a corner or rib in meter 110.
Further, in the exemplary embodiment, the thickness of dielectric material 208 varies throughout housing 312. Each ship-lap joint 540 and 545 between first portion 505 and second portion 510 provides an overlap of first portion 505 and second portion 510. Specifically, in this exemplary embodiment, first portion 505 and second portion 510 each have a thickness of about 1.2 millimeters at aperture 210. When the first portion 505 and the second portion 510 are assembled, first portion 505 and second portion 510 at least partially overlap at the major ship-lap joint 540 (along aperture 210) to create a total thickness of about 2.4 millimeters. Moreover, in this exemplary embodiment, first portion 505 and second portion 510 are structured such that the total thickness about the outside of housing 312 at a minor ship-lap joint 545 (opposite aperture 210) is less than about 1.2 millimeters. It should be appreciated that various methods of forming housing 312 may be used to provide one or more different thicknesses of housing 312 and/or dielectric material 208. In the exemplary embodiment, the major ship-lap joint 540 runs along a substantial portion of aperture 210. This is to provide a longer path for potential arcs between coil 204 and conductor 114.
In various other embodiments, the thickness of housing 312 and/or dielectric material 208 may be between about 0.5 millimeters and about 3.0 centimeters. In some embodiments, one or more thicknesses of housing 312 and/or dielectric material 208 are between about 1.0 millimeters and 6.0 millimeters. Further, in various embodiments, one or more thicknesses of housing 312 and/or dielectric material 208 are between about 1.0 millimeters and 4.0 millimeters. It should be appreciated that housing 312 and/or dielectric material 208 may have different thickness in other embodiments, potentially based on a method of assembly/fabrication, the characteristic(s) of a selected dielectric material, and/or desired performance characteristic(s). Further, other shapes, sizes, and/or joints for housing 312 may be used to at least partially enclosure coil 204, while positioning dielectric material 208 relative to coil 204 to perform consistent with one or more aspects of the present disclosure.
First portion 505 and second portion 510 also include a connection ring 525, an edge bevel 550, a side wall 530, and an outer wall 535. In the exemplary embodiment, the thickness of side wall 530 is less than that of combined thicknesses of first portion 505 and second portion 510 along aperture 210. Connection ring 525, on both first portion 505 and second portion 510 is where major ship-lap joint 540 of first portion 505 and second portion 510 connect. Connection ring 525 has the same thickness as the combined thicknesses of first portion 505 and second portion 510 at major ship-lap joint 540. Edge bevel 550 connects connection ring 525 to side wall 530. As edge bevel 550 goes from connection ring 525 to side wall 530, the thickness of edge bevel 550 slowly reduces. Where the thickness of edge bevel 550 starts at the thickness of connection ring 525 and slowly and consistently reduces to the thickness of side wall 530. Edge bevel's 550 consistent changes in thickness, prevents interruption in the electromagnetic field that may occur from abrupt changes in the amount of dielectric material 208 in the electromagnetic field.
When first portion 505 and second portion 510 are coupled, minor ship-lap joint 545 is formed along outer wall 535. Minor slip-lap joint 545 runs around the circumference of outer wall 535 when first portion 505 and second portions 510 are coupled. Both major ship-lap joint 540 and minor slip-lap joint 545 retain a clearance between first portion 505 and second portion 510. In the exemplary embodiment, this clearance is between 0.003 inches and 0.005 inches. The clearance is created when coil 204 is sandwiched between first portion 505 and second portion 510. Coil 204 and substrate 202 are sized so that when first portion 505 and second portion 510 are coupled around coil 204 and substrate 202, the fit creates the aforementioned clearance while housing 312 maintains a constant pressure on coil 204 and further prevents coil 204 from moving in relation to first portion 505.
In the exemplary embodiment, coil 204 includes an exemplary Rogowski coil. It should be appreciated; however, that sensor device 112 may include a coil other than a Rogowski coil. Further, aspects of the present disclosure are not limited to only being used with a Rogowski coil as described and illustrated herein.
First portion 505 includes retaining portions 515 and second portion 510 includes U-clips 520. U-clips 520 and retaining portions 515 attach first portion 505 to second portion 510.
In the exemplary embodiment, bobbins 902-912 are coupled together via hinged joints 916. More specifically, bobbins 902 and 904 are hingedly coupled to permit pivotal movement there between. In various embodiments, bobbins 902-912 may be linearly aligned to enable efficient winding of coil 204 and/or pivoted relative to one another to form a substantially circular shape, as illustrated in
Each of bobbins 902-912 of substrate 202 is a non-magnetic structure, such that bobbins 902-912 are constructed from one or more non-magnetic materials, including, for example, thermoplastic material, ceramic material, wood, material, or other kinds of suitable material(s). In this exemplary embodiment, each of bobbins 902-912 is fabricated from a dielectric material, potentially consistent with dielectric material 208. By use of a non-magnet substrate 202, cost savings may be realized over known sensor devices that include one or more magnetic cores. Moreover, in the exemplary embodiment, substrate 202 is shaped and/or sized to provide improved mounting within utility meter 110 and/or to a meter control board 117 (both shown in
In the exemplary embodiment, coil 204 is wound multiple turns on each bobbin 902-912. More specifically, in the exemplary embodiment, coil 204 includes a single magnet wire that enables coil 204 to be wound from bobbin 902 to bobbin 912 with several turns on each bobbin 902-912, and then wound back to bobbin 902 with additional turns on each bobbin 902-912. It should be appreciated that, in other embodiments, other different winding patterns on bobbins 902-912 may be used. Consistent with the above winding pattern across bobbins 902-912, a first end and a second end of coil 204 terminates at bobbin 902.
In addition to coil 204, in the exemplary embodiment, one or more shields are applied to substrate 202. Specifically,
In the exemplary embodiment, each shield 1005 and 1010 provides a Faraday shield. More specifically, in this exemplary embodiment, first and second shields 1005 and 1010 behave substantially consistent with a Faraday cage, in order to facilitate reducing common mode noise on the sensor device 112 and/or to provide a low-pass filter for high frequency noise filtering. As a result, first and second shield 1005 and 1010 facilitate improved performance in the context of one or more industry standards for electromagnetic interface (EMI) and/or electromagnetic compatibility (EMC).
During fabrication, a plurality of turns of a magnet wire are wound on each bobbin 902-912 from bobbin 902 to bobbin 912 to form first shield 1005. Coil 204 is then wound from bobbin 902 to bobbin 912 and back to bobbin 902 as described above. Subsequently, the magnet wire of first shield 1005 is wound from bobbin 912 back to bobbin 902 with a plurality of turns on each bobbin 902-912 to form second shield 1010. As such, in the exemplary embodiment, first shield 1005 and second shield 1010 are formed from a single magnet wire. It should be appreciated that first shield 1005 and second shield 1010 may include any suitable materials, such as, without limitation, copper, aluminum or other nonferrous conducting material. More generally, the shielding material may be formed as a sheet, a tape, a wire, a spray and/or any other form that enables bobbins 902-912 to include shields 1005 and 1010. As such, application of shields 1005 and/or 1010 may be formed, without limitation, via winding, wrapping, and/or spraying, for example. In various embodiments, first and second shield 1005 and 1010 may be formed separately from coil 204 and subsequently applied to coil 204.
One or more of the above described embodiments provide a highly-accurate sensor device. More specifically, the sensor devices, utility meters, and methods described herein may provide a highly-accurate sensor device that provides an expanded operating range with reduced calibration requirements over known coil sensors. For example, the disclosed dielectric material may provide reduced capacitance between a coil and one or more conductors, thereby providing improved accuracy across a range of currents and/or voltages. The improved accuracy may be realized with fewer calibration processes during manufacturing, resulting in reduced manufacturing cost and/or time. In another example, the disclosed shielding techniques provide improved rejection of EMI, originating from other electronics and/or tampering devices.
The above described embodiments provide systems and methods for preventing the coil of a sensor device from moving in relation to the conductor that the sensor device is measuring. More specifically, the sensor devices when used in utility meters will provide high accuracy measurement of current through conductors over a period of many years. By preventing the coil from moving, the calibration of the sensor devices will stay the same and ensure accurate measurements for many years.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
